1. Field of the Invention
The present invention is generally related to a muffler system for a marine propulsion apparatus and, more particularly, to an exhaust system that comprises a conduit that is shaped to form a water collection region, or water trap, and which can be configured in a single loop or multiple loop arrangement.
2. Description of the Prior Art
As is well known to those skilled in the art of marine propulsion systems, particularly sterndrive or inboard systems, cooling water is commonly injected into an exhaust gas stream and the combined exhaust gas and entrained water mixture is conducted through common conduits within the exhaust system. It is also well known to those skilled in the art that certain types of mufflers, sometimes referred to as xe2x80x9cwater liftxe2x80x9d mufflers, can provide an expansion chamber in which water can be collected and in which the collected water reduces the overall noise emitted by the internal combustion engine and its associated exhaust system. Known types of water lift mufflers have several negative characteristics. First, the expansion chamber of known water lift mufflers requires significant space in the region behind the internal combustion engine of a marine propulsion system. In addition, these mufflers can significantly increase the overall cost of the exhaust system. Furthermore, these mufflers are prone to a problem that is commonly referred to as xe2x80x9cwater ingestionxe2x80x9d because of the arrangement of conduits and components that are common in applications using water lift mufflers.
U.S. Pat. No. 4,019,456, which issued to Harbert on Apr. 26, 1977, describes a marine wet exhaust system and improvements in powered marine vessels. The system comprises an exhaust gas cooling water separation chamber, a gas collection chamber, and gas acceleration and gas flow-shaping conduit means. The entrance of the separation chamber is connectable to water coolant and gas exhaust tubes from a marine engine. The separation chamber is fitted with a water deflector disposed below the gas exit from that chamber, while a gas dam is disposed in the water exit from that chamber, the entrance and water exit going below the deflector level. The gas collection chamber is connected to the gas exit and a gas acceleration chamber, which tapers downstream, is connected to the gas collection chamber. A gas velocity tube is connected to and extends downstream of the gas acceleration chamber to cause exhaust gases to exit through the hull of a boat in which the system may be installed with sufficient force to penetrate the turbulent boundary layer of air around the boat hull when the boat is in motion, thus preventing the gases from passing back into the rear of the boat, due to the xe2x80x9cstation wagonxe2x80x9d effect. An air dilution tube can be connected to the gas velocity tube to provide a scarfing action by the exhaust gases, causing their dilution to below noxious levels. The system may include exhaust noise retarding means, such as a muffler and/or air barrier at the separation chamber entrance.
U.S. Pat. No. 5,746,630, which issued to Ford et al on May 5, 1998, describes a combination wet marine exhaust muffler and water separator. The combined wet marine exhaust muffler and water separator comprises a housing having a tangential inlet for inducing the exhaust flow to rotate about a lengthwise axis of the housing, a first outlet positioned along the axis for conducting dried exhaust gas from the housing, and a second outlet positioned near a bottom end of the housing and spaced from the tangential inlet and the first outlet for draining water from the housing.
U.S. Pat. No. 5,594,217, which issued to LeQuire on Jan. 14, 1997, describes an exhaust muffler for small marine craft. The muffler can be located in the rear portion of the bilge and straddle the drive shaft and the shaft log. The muffler has a shell formed from sides, ends, top and bottom walls. The bottom wall is provided with a concave depression to receive the shaft and shaft log. A preferred configuration of the depression is a semi-conical surface having a base proximate the inlet wall. Further, the top and bottom walls are configured to conform to the undersurface of the deck and the inside of the hull respectively. An inlet pipe, or a multiple number of inlet pipes, receive exhaust gases and water from the exhaust manifold of the craft engine and direct this combination into the muffler above a water pool. Gases pass through the water pool and exit through an outlet pipe or a plurality of outlet pipes. A downwardly extending conduit within the outlet pipes provides a correct amount of lift such that an amount of water exits the muffler which is the same as the amount entering. Because of the shape and construction, the muffler can be placed within the bilge of the craft in a space that is normally not used.
U.S. patent application Ser. No. 09/604,147 (M09434) which was filed by Erickson on Jun. 27, 2000 and titled xe2x80x9cExhaust Elbow With a Water Trap for a Marine Propulsion Systemxe2x80x9d describes an exhaust elbow for a marine propulsion exhaust system which is provided with a water trap section that defines a water collection cavity. Within the water trap section, a barrier extends downward into the water collection cavity to define first and second exhaust passages. When water begins to collect in the water collection cavity, the cross sectional area of the exhaust passage is reduced and the velocity of exhaust gases passing through the exhaust passage is increased. The water collection cavity is shaped to be easily cleared when exhaust gas pressure increases as the engine speed increases.
The patents described above are hereby expressly incorporated by reference in the description of the present invention.
It would be significantly beneficial if a muffler could be provided for a marine propulsion system in which the components of the muffler were relatively inexpensive, but would provide the noise reducing benefits of a water lift muffler. It would be particularly beneficial if a muffler of this type could be provided in which the basic components required to construct the muffler were relatively inexpensive and readily available.
A muffler for an exhaust system of a marine propulsion device made in accordance with the present invention comprises an ingress conduit which is attachable in fluid communication with an exhaust manifold of an internal combustion engine. The muffler, itself, does not require the presence of the exhaust manifold, but is designed to be associated with an exhaust manifold of an engine. The muffler further comprises a water collection cavity that is connected in fluid communication with the ingress conduit. A muffler made in accordance with the preferred embodiment of the present invention further comprises an egress conduit connected in fluid communication with the water collection cavity, whereby water entrained in an exhaust stream from the engine is induced to accumulate within the water collection cavity, within a lowest region of the ingress conduit, and within a lowest region of the egress conduit in response to the exhaust stream flowing sequentially from the exhaust manifold, through the ingress conduit, the water collection cavity, and the egress conduit. The ingress and egress conduits are connected in fluid communication with each other only indirectly through the water collection cavity. The water collection cavity defines a confined fluid path between the ingress conduit and the egress conduit.
In a particularly preferred embodiment of the present invention, the water collection cavity is a generally tubular passage between the ingress and egress conduits. The exhaust stream flows sequentially downward through the effective length of the ingress conduit, generally horizontally through the effective length of the water collection cavity, and upward through the effective length of the egress conduit.
The present invention, in certain embodiments, can further comprise a generally horizontal intermediate conduit connected in fluid communication with the egress conduit, with the egress conduit being connected in fluid communication between the water collection cavity and the generally horizontal intermediate conduit. The muffler can further comprise a final exhaust conduit connected in fluid communication with, and extending downward from, the generally horizontal intermediate conduit.
When used in a marine vessel, the muffler of the present invention further comprises an internal combustion engine and an exhaust manifold attached to the engine for directing the exhaust stream from a plurality of cylinders of the internal combustion engine to the ingress conduit. The exhaust manifold is normally connected in fluid communication with the ingress conduit.
An exhaust muffler made in accordance with the present invention comprises a first conduit loop which is attachable in fluid communication with an exhaust manifold of an internal combustion engine. The first conduit loop sequentially extends downward through a first section of the first conduit loop from the exhaust manifold and then upward through a second section of the first conduit loop. A central portion of the first conduit loop defines a first water collection region between the first and second sections of the first conduit loop, whereby an exhaust stream flows sequentially from the exhaust manifold, downward through the first section of the first conduit loop, through the water collection region, and then upward through a second section of the first conduit loop.
Certain embodiments of the present invention can further comprise a second conduit loop which is attachable in fluid communication with the first conduit loop, the second conduit loop sequentially extending downward through a third section of the second conduit loop from the first conduit loop and then upward through a fourth section of the second conduit loop. A second central portion of the second conduit loop defines a second water collection region between the first and fourth sections of the first and second conduit loops, whereby an exhaust stream flows sequentially from the exhaust manifold, downward through the first section of the first conduit loop, through the first water collection region, upward through the second section of the first conduit loop, through the third section of the second conduit loop, through the second water collection region, and finally through the fourth section of the second conduit loop.
A muffler system for a marine propulsion system made in accordance with a particularly preferred embodiment of the present invention comprises a channel for conducting a fluid mixture of exhaust gas and water from an exhaust manifold from an engine. The channel has an inlet, an outlet, and a first transitional section connecting the inlet and the outlet. The first transitional section is positioned below the inlet and the outlet by a sufficient distance to form a first liquid collection region through which the exhaust gas must pass as it flows from the inlet to the outlet. Although the present invention will be described below as a generally U-shaped channel configuration, it should be understood that a V-shaped configuration could also provide the inlet, the outlet, and a first transitional section positioned below the inlet and outlet by a sufficient distance to form a first liquid collection region through which the exhaust gas must pass as it flows from the inlet to the outlet.
The muffler system can further comprise a second transitional section connecting the inlet and the outlet. The second transitional section is positioned below the inlet and the outlet by a sufficient distance to form a second liquid collection region through which the exhaust gas must pass as it flows from the inlet to the outlet. The first and second transitional sections are connected in serial fluid communication with each other to direct the exhaust gas sequentially from the inlet, through the first liquid collection region, through the second liquid collection region, and through the outlet.
Particularly preferred embodiments of the present invention, when used within a marine vessel, further comprise the exhaust manifold of the engine which is connected in fluid communication with the inlet and an internal combustion engine that is connected, through the exhaust manifold, in fluid communication with the inlet.